Two high affinity calcium-binding proteins have been isolated from brain adrenal medulla, testes and electric tissue. One of these proteins, CBP II is an activator of several calcium-dependent brain enzymes including cyclic nucleotide phosphodiesterase and adenylate cyclase. We propose that the role of this protein is to entrain the chemical activities of the neuron to the pace of electrical activity; the key event in this process would be calcium influx and the binding of calcium to CBP II. We have described the cellular localization of CBP II in brain and are actively investigating its synthesis and phosphorylation.